I think that yes, some folks were always going to dislike the change. That's what you're up against when you decide to change one of the most incredible and popular theme park attractions ever created. For Disney, the stakes could not have been higher-- and I think not fully appreciating this was their first mistake.
But look back on these boards and elsewhere, and a lot of folks, even many who expressed dislike over the initial decision, transitioned into the "let's wait and see" camp. Let's be fair and give Disney the benefit of the doubt.
Disney then acknowledged the stakes were high and began to tout how incredible the new ride would be, releasing teasers of animatronics and storylines and even admitting Bob Iger wanted improvements and that improvements were being made. Their message: "We understand. Don't worry. We hear you. We've got this."
Perhaps they set expectations too high; perhaps (as many folks have been arguing) they are simply completely out of touch.
The issue is larger than the ride itself at this point. Disney has been responsible for a growing number of recent and massive missteps. Starcruiser, Harmonious, EPCOT's transformation, a lifeless and sterile Star Wars land, disrespecting sight lines, instituting a firm caste system in the form of Genie+, longer lines, higher prices, endless upcharges, confusing apps, needless complications, questionable ride reliability, countless examples of poor show and shoddy maintenance, only one waterpark open at a time, destroying highly themed resort environments by supplanting or replacing incredibly themed architecture with bland and generic construction, a botched tile job in Morocco, a DJ in the train station at the MK... the list goes on.
So with TBA, the stakes could not have been higher and the consensus is mixed at best. To respond by simply calling a thread "miserable" tracks with the growing effort on these boards to dismiss negativity as whining, or hyperbole, or expressing a lack of imagination.
Read the criticisms in this thread. Yep, some are driven by an agenda, but the *vast* majority are basing their opinions on solid criticism and have expressed those criticisms in specific and constructive terms.
A miserable thread is what you get when the stakes are unbelievably high and you manage to overpromise and underdeliver.
It's not just TBA. A lot of folks, lifetime fans and paying customers who invested financially and emotionally in a brand that charges a lot but promises even more... have reached the end of their patience. And it shows.